Wireless telephones, such as mobile/cellular telephones, cordless telephones, and other consumer audio devices, such as mp3 players, are in widespread use. Performance of such devices with respect to intelligibility can be improved by providing noise cancelling using a microphone to measure ambient acoustic events and then using signal processing to insert an anti-noise signal into the output of the device to cancel the ambient acoustic events.
A noise cancellation system that uses feedback noise cancellation may suffer from an effect known as “howling.” Howling often occurs when a user of a device having noise cancellation places an earbud in such user's ear and adjusts the earbud against the pinna of the ear. Howling often manifests itself audibly as a narrowband sound that continues to grow quickly over a short time. A howl may often occur when the earbud is pressed so tightly against the user's pinna with such a large pressure that the response of the speaker of the earbud becomes stronger in a particular frequency band than was anticipated when the device's feedback noise cancellation system was designed. The howl may go away once the user reduces pressure of the earbud against the pinna. Because howling leads to poor customer experience, systems and methods to reduce or eliminate howling are desired.